Electric furnace



Sept. 4, 1923.

1,467,044 E. F. KIEFER ELECTRI C FURNACE Filed June 11, 1920 mvantoz EM T. b-

D 5 $2", W Wil -N,

Patented Sept. 4, 1923.

UNITED STATES PATENT OFFICE.

EDWIN F. KIEFER, OF GLEVELAND, OHIO, ASSIGNOR TD NATIONAL CARBON COMPANY,

. INC, CORPORATIGN OF NEW YORK.

ELECTRIC FURNAEE.

Application and ."func 11, 1920. Serial No. 385,164.

-T|0 all whom it may concern:

Be it known that l, EDWIN F. Krsrnn, a citizen of the United States, residing at Cleveland in the county of Cuyahoga and State of Ohio, have invented certain new and useful Improvements in Electric Furnaces, of which the following is a specification.

This invention relates to electrically heated furnaces, particularly those of the cruch lole type, the object of the invention being to provide a simple and highly efiicient construction of this character, well adapted for the melting of metals, the manufacture and melting of alloys, and many other purposes. For a full understanding of the invention reference is made to the accompanying drawing wherein Figure 1 is a vertical central section of a simple construction in accordance with my invention, showing also the appropriate electric circuits;

Figure 2'is a similar section on line 2-2 of Figure l; and

Figure 3 is a similar View of a modified furnace with multiple heating units.

Referring to said drawing, 10 represents a crucible of refractory material, the nature I of which Willof course depend upon the operation to be performed and the temperature required. Fire-clay, alumina, magnesia, zirconia, and other non-conductive refractory materials are all'suitable. Carbon or graph" its may also be used, with the necessar precautions to avoid grounding of the e ectric circuit.

In the ,rorrns chosen for illustrationthe base of the crucible, or bottom Wall of, the furnace, is constructed with a transverse portion 11. whichprojects upwardly into the heating chamber in such manner as to present an ex ruded heating surface therein, this projecting portion being apertured as indicated at 12 to receive the heating elemcnt. This latter, in its preferred form, comprises a conductive cylinder 13 which may be of carbon or graphite constituting one electrode, and a rod or cylin er bl con-- centric therewith, constructed. of similar material, and constituting the other electrode. 'lhese electrodes are maintained in their proper spaced relation by annular insulating bushings 16. which may consist of any suit able electrical. and thermal insulating, inatcrial as for xix-am le ire-clay, zirconia,

alumina, etc. 17 and 18 indicate respectively the current terminals of the two electrodes. The furnace-1s most advantageously opera'ted on the arc principle, the are striking multiplied as desired and the furnace chamber may be given any form apprdpriate for its intended use.

The constructions shown possess many advantages, among which the following may be mentioned:

1. The heating units are wholly shielded from the charge by a thin refractory Wall which presents an extended heating surface to the charge and may have a very high thermal conductivity. The contamination or" the charge by carbon from the electrodes is thus Wholly avoidedf 2. The heat is advantageously applied at thebottom of the charge, which in case of fluid melts is thoroughly mixed by the resulting convection currents.

3. The heating units are simple in construction and may be readily removed and replaced.

4. The heating elements of the referred form illustrated are quite uniform y heated and are not subject to rapid deterioration. Since the electric discharge occurs within the closed annularinterspace 15, this interspace quickly becomes filled with highly heated neutral gas, whereby the heat is not only evenly distributed, but oxidation of the electrodes is prevented.

5. The construction lends itself to a ready and accurate control of the furnace temperature.

1. An electric furnace of the arc type, connirising a refractory Wall provided with any aperture, and a heating element insertable in such aperture, said heating element comprising electrodes in arcing relation to each other in a closed interspacc therehctween.

2. Construction according to claim. 1,

wherein the electrodes consist of concentric members separated by a closed annular interspace.

3. An electric fnrnn'ce comprisinga heating chamber provided with a bottom having a portion projecting upwardly into said clnunber to present an extended surface within said chamber, and electric heating means Within such projecting portion.

4 Construction according to claim 3 wherein said heating means comprises electrodes in arcing relation to each other.

An electric furnace comprising a heating chamber provided with a Wall having a plurality of inwardly jnojecting portions presenting an extended heating surface Within said chamber, and electric heating means within each oi. said portions.

(3. An electric heating element comprising the combination of a: hollow electrode, and an electrode projecting into and having a portion enclosed in said hollow electrode and in arcing relation to the inner surface thereof.

In testimony whereof; I nth); any signature,

EDl/VIN F. KHSFER. 

